Cartridges used with firearms are commonly classified as center-fire or rim-fire, depending on the position of the "primer" in the cartridge. As used herein, "rim-fire" particularly refers to cartridges which are of an enlarged rim configuration, i.e., which have a rim section of a greater diameter than the diameter of the body portion of the cartridge. This type of cartridge has created a number of problems for the design of magazines intended to house such cartridges. In particular, it is difficult to house such cartridges in a space-efficient manner without creating a jamming problem.
It is known that the length of a magazine designed to house a given number of cartridges can be reduced by storing the cartridges in two columns, such as the arrangement depicted in German Pat. No. 90189 issued Mar. 21, 1896 to Clausius. It is further known that the width of two-column magazines can be reduced by offsetting the columns as shown in U.S. Pat. No. 4,112,817, issued Sept. 12, 1978 to Bourlet.
Such two-column arrangements require some means for feeding the cartridges one at a time into the firearm in an orderly fashion. Previous methods have attempted to accomplish this by tapering the interior of the magazine to force two or more columns into a single column, before feeding into the firearm. Such an approach is depicted in U.S. Pat. No. 2,217,848, issued Oct. 15, 1940 to Schillstrom; U.S. Pat. No. 3,345,771, issued Oct. 10, 1967 to Silsby; and U.S. Pat. No. 3,604,142, issued Sept. 14, 1971 to Silsby. These patents do not recognize, or disclose how to solve, certain problems inherent in a tapering approach to a single file feed from a multiple column magazine. In particular, these patents do not disclose how to control the lateral force exerted on the cartridges by the side walls so as to prevent jamming, and yet keep the magazine length to a minimum.
Furthermore, none of these references are directed to rim-fire cartridges and the problems associated therewith. Rim-fire cartridges are particularly difficult to house in a multiple column magazine because the rims must, at least for the uppermost cartridges, be in a relationship so as not to interfere with one another upon extraction of the uppermost cartridge from the magazine. Further, this provision for noninterference of rims must itself be compatible with other provisions for avoiding jamming as the two-column relationship is changed to a single file relationship.
Another method of housing rim-fire cartridges in a strictly single file relationship is shown in U.S. Pat. No. 4,127,954, issued Dec. 5, 1978 to Hausmann. This patent, however, neither recognizes nor discloses how to solve the problems associated with double column storage of rim-fire cartridges and the transition from a double column of cartridges to a single file arrangement of cartridges.